1. Field of the Invention
The present invention relates to an electron source substrate in which a plurality of electron-emitting devices are arranged in a matrix pattern, and display apparatus using it.
2. Related Background Art
As the electron-emitting devices used in the display apparatus of this type, there are two types of devices: thermal electron sources and cold cathode electron sources. The cold cathode electron sources include field emission devices, metal/insulator/metal devices, surface conduction electron-emitting devices (hereinafter referred to as SCE devices), and so on. The SCE devices will be described herein.
The SCE devices are devices making use of the phenomenon in which electrons are emitted when an electric current is allowed to flow through a thin film of a small area formed on a substrate and in parallel to the film surface. FIGS. 19A and 19B show the configuration of the M. Hartwell's device as a typical device configuration of the SCE devices. FIG. 19A is a top plan view of the device and FIG. 19B a side view thereof.
With reference to FIGS. 19A and 19B, this SCE device is constructed in structure in which a pair of device electrodes 142, 143 having the device electrode spacing L and the device electrode length W are formed on a substrate 141 of glass or the like, an electroconductive thin film 144 is formed so as to connect these device electrodes 142, 143, and an electron-emitting region 145 is formed near the center of the electroconductive thin film 144.
Since the SCE devices are simple in structure and easy in production, they are advantageous in permitting a lot of devices to be arrayed over a large area. Therefore, they are readily applicable to the display apparatus and a variety of display apparatus have been proposed heretofore.
The following will briefly describe the structure and operation of an ordinary display apparatus provided with an electron source substrate in which the SCE devices are arranged in a matrix.
FIG. 20 is a perspective view showing a portion of a conventional display panel extracted. This display panel is provided with a face plate 159 having a phosphor 150 on a lower surface and a rear plate 151 opposed thereto. In the rear plate 151, a plurality of electron-emitting devices 156 to 158 are formed each in a configuration consisting of a pair of device electrodes 152, 153 and an electroconductive thin film 154 formed so as to connect them and having an electron-emitting region 155 near the center. These electron-emitting devices 156 to 158 are similar to the SCE devices shown in FIGS. 19A and 19B.
In this display panel, when a device voltage Vf of ten and several Volts is placed between the device electrodes 152, 153, electrons are emitted from the lower potential side of each electron-emitting region 155 and part of electrons impinge upon the face plate 159 serving as an anode to which a voltage of several kV is applied, thereby inducing emission of light from the phosphor 150.
For reference, the following provides some of related technologies developed by Assignee, as technologies about the above-stated SCE devices.
Japanese Patent Applications Laid-Open No. 09-102271 and No. 2000-251665 detail production of the SCE devices by the ink jet forming method. Japanese Patent Applications Laid-Open No. 64-031332 and No. 07-326311 detail examples of the matrix arrangement of the SCE devices. Furthermore, Japanese Patent Applications Laid-Open No. 08-185818 and No. 09-050757 describe wiring forming methods of the electron source substrate provided with the SCE devices, and Japanese Patent Application Laid-Open No. 06-342636 and others detail driving methods. Japanese Patent Applications Laid-Open No. 02-247936, No. 02-247937, and No. 07-326283 disclose placement of a resistor element in series to the SCE device in order to enhance uniformity of characteristics of the electron-emitting device.
The display apparatus using the conventional SCE devices described above had the problems as described below, however.
When the conventional display panel shown in FIG. 20 was driven, for example, by applying the device voltage Vf of ten and several Volts between the device electrodes 152, 153 of the electron-emitting device 158 to cause emission of electrons therefrom and accelerating the emitted electrons by the acceleration voltage of several kV, there sometimes occurred a short circuit between the lower potential side and the higher potential side of the electron-emitting device because of adsorbates near the electron-emitting region 155, or discharge due to local degassing, or the like. On that occasion, an over current sometimes flowed through the electron-emitting device 158 to break the electroconductive thin film 154 and the electrodes 152, 153. Furthermore, the gas evolved on that occasion induced discharge between the anode and the electron-emitting region 155 to break the electroconductive thin film 154 and the electrodes 152, 153 and an abnormal voltage was also applied through wiring to the other electron-emitting devices 156, 157 electrically coupled, thereby causing deterioration of these devices. Conventionally, such phenomena posed the problem that nonuniformity of luminance or the like resulted in degradation of quality of displayed images.
If the voltage applied to the anode is increased, discharge will occur between the electron-emitting region of the electron-emitting device and the anode. The number of devices damaged by this discharge tends to increase with increase in the anode voltage. The reason for it is as follows: an abnormal current flowing upon the discharge becomes larger, so as to increase the degree of the damage to the device and increase the abnormal voltage applied to the wiring, thereby increasing the number of devices affected through the wiring. For this reason, it was impossible to adequately increase the anode voltage heretofore, and this was a cause of decrease in the luminance of the display panel.
The problems as described above did not allow the surface conduction electron-emitting devices to be positively applied in industries though they had the advantage of simple device structure.